Lacunar ischaemic stroke syndromes are clinically, pathophysiologically, and prognostically distinguishable from cortical ischaemic stroke syndromes. Could cerebrovascular transient ischaemic attacks (TIAs) share similar heterogeneity? 130 patients with TIAs were prospectively studied, 71 of whom underwent carotid angiography. Symptoms were associated with a 50% or greater stenosis of the ipsilateral internal carotid artery in 36 (67%) of 54 patients with presumed cortical TIAs, but in only 1 (6%) of 17 patients with presumed lacunar TIAs (p <0.0001). These findings support the view that cortical TIAs are associated with ipsilateral extracranial internal carotid artery atheromatous disease, whereas patients with lacunar TIAs may have absent or insignificant large-vessel disease, and probably intracranial small-vessel disease. Accurate distinction between lacunar and cortical events may have implications for investigation and treatment of patients with TIAs.